The nematode Caenorhabditis elegans is a choice model system is which to study the genetic specification of invertebrate muscle and the developmental control of eukaryotic gene expression. The in vivo relationships between the protein components of muscle will be investigated through the isolation of mutants and the biochemical characterization of their molecular defects. The immediate goals of this proposal are: 1. to describe more fully the several isozymic forms of muscle myosin; 2. to isolate recombinant DNA clones containing DNA sequences corresponding to myofilament protein structural genes; 3. to genetically identify additional components of muscle, especially those involved in regulating the tissue-specific expression of myofilament proteins; 4. to analyze specific molecular details of mutant strains. The fundamental plan is to gain insight into the developmental and regulatory relationships between these genes by isolating and biochemically analyzing mutations that affect those relationships. The techniques of genetic analysis are central to this plan. Biochemical characterization of mutant strains will indicate the molecular details. Our long range objectives are to elucidate the cellular control mechanisms that are responsible for tissue-specific expression of myofilament proteins. The health relatedness of this work derives from its contribution to a more thorough understanding of basic cellular control mechanisms, in as much as defects in these control mechanisms lead to human disease.